Deterrence and the Death Penalty: Partial Identification Analysis Using Repeated Cross Sections

Objectives

Researchers have used repeated cross sectional observations of homicide rates and sanctions to examine the deterrent effect of the adoption and implementation of death penalty statutes. The empirical literature, however, has failed to achieve consensus. A fundamental problem is that the outcomes of counterfactual policies are not observable. Hence, the data alone cannot identify the deterrent effect of capital punishment. This paper asks how research should proceed. We seek to make transparent how assumptions shape inference.

Methods

We study the identifying power of relatively weak assumptions restricting variation in treatment response across places and time. We perform empirical analysis using state-level data in the United States in 1975 and 1977.

Results

The results are findings of partial identification that bound the deterrent effect of capital punishment. Under the weakest restrictions, there is substantial ambiguity: we cannot rule out the possibility that having a death penalty statute substantially increases or decreases homicide. This ambiguity is reduced when we impose stronger assumptions, but inferences are sensitive to the maintained restrictions.

Conclusions

Imposing certain assumptions implies that adoption of a death penalty statute increases homicide, but other assumptions imply that the death penalty deters it. Thus, society at large can draw strong conclusions only if there is a consensus favoring particular assumptions. Without such a consensus, data on sanctions and murder rates cannot settle the debate about deterrence. However, data combined with weak assumptions can bound and focus the debate.     

Proactive Policing: a Summary of the Report of the National Academies of Sciences,Engineering, and Medicine

This paper provides a summary of our report for the National Academy of Sciences, Engineering, and Medicine on proactive policing. We find that there is sufficient scientific evidence to support the adoption of many proactive policing practices if the primary goal is to reduce crime, though the evidence base generally does not provide long-term or jurisdictional estimates. In turn, we conclude that crime prevention outcomes can often be obtained without producing negative community reactions. However, the most effective proactive policing strategies do not appear to have strong positive impacts on citizen perceptions of the police. At the same time, some community-based strategies have begun to show evidence of improving the relations between the police and public. We conclude that there are likely to be large racial disparities in the volume and nature of police–citizen encounters when police target high-risk people or high-risk places, as is common in many proactive policing programs. We could not conclude whether such disparities are due to statistical prediction, racial animus, implicit bias, or other causes.